The present invention relates to a new bi-component synthetic dyeable carpet face yarn that is manufactured using the sheath-core melt spinning process. This carpet yarn is an endless multifilament yarn comprised of a plurality of individual uniformly sheath-cored filaments having a dyeable sheath of virgin polyamide and a polymer core that can not be dyed using standard atmospheric pressure carpet dyeing methods. This yarn is a less expensive substitute for 100% Polyamide tufted carpet face yarn. It is made by a process that can use substantially reclaimed resin making it an invention that is both economically and environmentally beneficial.
The present invention finds a primary application in the tufted carpet industry. The tufted carpet industry uses undyed yarns as face yarns to create tufted carpet greige goods. In the manufacture of tufted carpeting, the face yarns used in the process, account for at least 68% of the cost of the finished product. Face yarn constitutes the major cost component in the manufacture of carpet. The other major costs to manufacture carpet are the dyeing of the carpet or greige goods. Carpets are almost always dyed by a standard atmospheric dyeing process. In the dyeing process, the carpet is subjected to a bath of dyes, chemicals and water at elevated temperatures. The dye attaches chemically to the yarn and the result is a desirable color shade. Yarns used constitute the major portion of expense while the dyeing of the fabric constitutes the second most expensive manufacturing step.
There are two common types of synthetic dyeable yarn available to the tufted carpet industry, Polyester and Polyamide. The Polyamide yarns are dyeable at standard atmospheric pressure eliminating expensive pressure vessels and harsh chemical carriers needed to dye Polyester. Therefore, the tufted carpet industry uses 90% polyamide as face yarns to manufacture carpet dyeable at atmospheric pressure. Polyamide yarns are dyeable because amine ends are used in its manufacture. These amine ends are receptive to the most common acid dyes used in the tufted carpet industry. Polyamide yarns are called by the generic trade name nylon. There are two common trade names for nylon, Nylon 6 or Nylon 6/6. Both are dyeable using standard atmospheric pressure in concert with acid dyes. They are well known to those skilled in the art.
As Reader says in U.S. Pat. No. 4,406,310 "Since carpets must be both functional and aesthetic the characteristics of the face yarns inserted into the fabric and the ability to apply desired colors to such yarns and tufted carpets and the tufting design are very important in determining marketability of the final carpets." In addition to ease of dyeing carpeting must withstand repeated stress under various traffic pressure. Because Nylon stands up to heavy traffic and its ease of dyeing, it is the yarn of choice in the tufted carpet industry. Nylon is the primary raw material for approximately 68% (1.2 billion pounds) of the total synthetic tufted carpet industry.
Synthetic fibers and yarns are all based on the huge petrochemical industry. Nylon is a direct product of the refining process and increases in price in direct proportion to the price of oil. Nylon is only available from a small number of large manufacturers. This limited number of suppliers is due to the capital intensive equipment required to polymerize nylon. Although it is desirable to produce a less expensive substitute for carpet nylon. The solution to this problem has been difficult to achieve.
Specifically, to qualify as a nylon substitute face yarn in the tufted carpet industry, the yarn must have the following characteristics:
1. superior recovery from crushing or compression PA1 2. The ability to be tufted at high speeds PA1 3. The ability to apply desired color on conventional dyeing equipment at atmospheric pressure PA1 4. Strength to resist heavy foot traffic PA1 5. A good bulking characteristic to give coverage with out using too much material (texturing potential)
No other synthetic carpet materials except nylon possess all the previously named five desired qualities.
The manufacturer of tufted nylon carpet can achieve many desirable color effects from undyed greige goods. For example, the carpet can be dyed into many different shades of solid colors, printed with floral or geometric designs, or sprayed with computer assisted equipment for tonal effects. While using nylon other special effects can be achieved in the dyeing and treatment of the yarn. This includes the application of stain repellents, anti-microbial and multicolored space dyeing.
It is known in patents that a sheath core system of manufacture may be used to make a sheath-core bi-component fibers. The following is a review of prior art concerning sheath-core patents.
Sheath-core techniques using different cross sections and differing materials to produce desired yarn characteristics are well known in the art. The Matsui U.S. Pat. No. 3,700,544 clearly teaches improved flexural rigidity due to an appropriate non-circular shape given to the cross section of the core. Matsui's examples all specify quenching the drawn filaments in 100 centigrade water for between ten and fifteen minutes. Those skilled in the art would recognize these as laboratory conditions impractical for the commercial production of carpet yarn.
Lin Fa Lee U.S. Pat. No. 3,992,499 shows that it is possible to extrude two filaments of differing dyeability using a sheath core system of feeding two molten polymers to a special spinnerette. It is clear that the invention teaches how to dye heather effects for apparel by varying the amount of polymer having differing dye receptors. The yarn sizes in each example limit the use of the invention to apparel applications. This invention does not teach any practical carpet yarn applications to one skilled in the art.
Hull U.S. Pat. No. 3,803,453 teaches that a polyethylene sheath with a core of carbon can be co-extruded with nylon to create a synthetic filament having a superior conductive property to eliminate static. The sheathed core filament is a minor portion of total yarn bundle. FIG. 2. shows that only a small percentage of cored filaments are required in order to eliminate static electricity.
Leeuwen et al. U.S. Pat. No. 4,474,617 teaches a bi-component multifilament that has a pigmented core while retaining a high tenacity suitable for use in seat belts, fishing nets and ropes. The object is to protect seat belt, nets, and rope manufacturing equipment from unnecessary pigment abrasion. This invention has no applicability to the manufacture of carpet face yarn.
Saito et al. U.S. Pat. No. 4,987,030 teaches that by melt spinning a bi-component sheath core process using a high intrinsic viscosity polyethylene terephthalate core and a polyamide sheath composed mainly of polyhexamethylene adipamide (Nylon 66) it is possible to produce a superior tire cord yarn that has excellent adhesion to rubber. The specifications call for a core material using a high IV of preferably 0.90 and yielding a high tenacity conjugated fiber. The high intrinsic viscosity raw material which Saito uses is much too expensive to be used in the manufacture of carpet yarn. The high tenacity requirement for tire cord yarn is not required for a carpet face yarn.
Schipper et al. U.S. Pat. No. 4,019,311. uses the principles of bi-component sheath-core and side by side extrusion. The concept clearly states that a stretch ratio of 1:1.25 to 1:2.5 be maintained in order to achieve the desired results. The invention uses the second stage of stretching to break filaments causing them to twist around the other dissimilar filaments thus producing a yarn that feels as if it were mechanically spun from staple tow. Schipper relies on using two filaments that have different stretch potentials, thus one is fully stretched and breaks when drawn further in a second step while the other does not break and is used as a vehicle to carry the broken filaments. This is shown clearly in FIG. 4 where an edge roller is used to draw stretch and break some filaments. While this concept may be useful in the apparel and sweater trade, the weakness of the yarns produced using this method would prohibit them from being used as a carpet yarn.
While teaching specific sheath-core technology techniques the forgoing patents do not address the characteristics necessary for the manufacture of a dyeable carpet face yarn. More specifically, both cost and performance characteristics of each of the above prohibit teaching or suggesting use as commercial carpet yarns.